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Astronomy Q&A Live Stream

Astronomy Q&A Live Stream

On April 9 I hosted my first Astronomy Q&A live stream on Facebook. I responded to questions about the planets and then to questions made to me by viewers of the live stream.

It was fun but wore me out. If I do another live stream in the future, I may reduce the time or have a moderator/interviewer to make the stream more dynamic. If you have any other suggestions, feel free to let me know.

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Astronomy Q&A Live Stream Announcement

Astronomy Q&A Live Stream Announcement

After getting your feedback, I’ve scheduled my first Astronomy Q&A live stream for Monday, April 9, at 6:45 pm Pacific Time via Facebook Live.

I’ll start out by answering questions about the planets that middle- and high-schoolers of Summit Academy in Cottonwood asked me recently when I spoke to them about the Origin of the Universe. Then I’ll take on any questions that viewers of the live stream submit. I expect about ten to fifteen viewers, so there is a good chance I will be able to respond to all questions. Hope you can join!

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Why Does Spring Start March 20?

Why Does Spring Start March 20?

The first day of spring and the first day of fall happen on equinoxes, when the plane of Earth’s equator passes through the Sun’s center. Day and night are appoximately (but not exactly) of equal length.

Before Julius Caesar introduced his calendar in 45 BC in order to approximate the tropical (solar) year, the seasons had never been fixed to calendar dates. (In this blog post, I won’t go into all the details about the different ways of measuring years, which I have done elsewhere.) In the Roman system, calendar years were at first only 304 days (the Calendar of Romulus), which were split into ten months, March being the first. This is why the our months September through December are misaligned with the numbers 7 (septem), 8 (octo), 9 (novem), and 10 (decem). Through the reform of King Numa Pompilius around 700 BC, January and February were added. At this time, however, some months had fewer days than they do now, and the year consisted of only 354/355 days. To make the calendar follow the seasons a little more closely, the Pontifex Maximus (the head of the main college of priests in ancient Rome) was given the authority to insert an extra month between February and March. Since the Pontifex Maximus ended up wielding this tool for political purposes, it was not long before the seasons and year were misaligned. To re-align the year, Julius Caesar made 46 BC last 445 days, and then implemented his new calendar on January 1, 45 BC.

In 45 BC, March 25 was the first day of spring. The Julian year (365.25 days), however, is slightly longer  than the tropical year (365.24217 days). This caused the seasons to drift forward in the calendar. After a few centuries, spring was beginning on March 21, when a decree from the Council of Nicaea (AD 325) included the vernal equinox as part of the equation for determining the date of Easter (the Sunday after the first Full Moon after the vernal equinox) so that Christians throughout the world would celebrate Easter on the same day. No change was made to the calendar at this time, however, and the seasons continued to drift. By the time of the Gregorian calendar reform in 1582, the vernal equinox fell on March 11. Pope Gregory XIII wanted to bring it back to where it was when at the time of the Council of Nicaea. So in 1582, to bring the seasons back on track, ten days were skipped. Those who heeded the Pope’s decree in 1582 went to bed Thursday, October 4, and woke up Friday, October 15. To keep the seasons on track, the rule for leap years was also changed: years that are multiples of 4 have leap days (just like in the Julian calendar), except years that end in 00, except years whose digits before the 00 are multiples of 4. This meant that the years 1600 and 2000 were leap years (16 and 20 are multiples of 4), whereas the years 1700, 1800, and 1900 were not leap years. As a result, the Gregorian year is 365.2425 days, still not matching totally to the tropical year, but a good deal closer than the Julian calendar. Since the Gregorian calendar reform came from the Catholic Church, non-Catholic countries delayed even centuries in making the switch (e.g., England in 1752, Russia in 1918). This, however, is the calendar the Western world follows today.

The vernal equinox falls on March 20 this year, but some years it will fall on March 19; some years, on March 21. The oscillation is mainly due to leap days being observed in some years and not in others. The first days of other seasons differ by plus or minus a day as well. Here’s a chart that shows the transition times between seasons.

Although the 25th of March, June, September, and December no longer coincides with an equinox or solstice, it still keeps some of the meaning that was associated with its previous status. In Christianity, December 25, of course, is the birth of Christ. Nine months prior, March 25, is the feast of the Annunciation to Mary and Incarnation of the Son of God, as well as the traditional date for the Crucifixion. No wonder J.R.R. Tolkien, a devout Catholic, picked March 25 as the date for the destruction of the One Ring.

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The “We’re Not Special” Ideology

The “We’re Not Special” Ideology

“We’re not special” is not a scientific statement. It’s an opinion. It’s a simple way of expressing what has become known as the Copernican principle. Copernicus himself did not explicitly hold this when he realized Earth was likely not the physical center of the universe. In the generation after Copernicus, isolated thinkers like Giordano Bruno interpreted this as a demotion of Earth. It did not become such a widespread view until recently.

Carl Sagan asked in the original Cosmos, “Who are we? We find that we live on an insignificant planet of a humdrum star lost in a galaxy tucked away in some forgotten corner of a universe in which there are far more galaxies than people.” Sagan had requested that, as Voyager 1 left the solar system in 1990, it turn its camera around to take one last picture of Earth. Presenting this image before an audience at Cornell, he reflected on all the people that have lived on Earth, “a mote of dust suspended in a sunbeam.” His speech is worth reading in full. Interwoven in the beautiful prose, however, is the assumption that the Earth is unimportant since it’s just a dot in this image.

Just because the Earth is small when it is compared to the vastness of space does not make it insignificant. Assumptions of the homogeneity and isotropy of the universe lead to accurate scientific cosmological models. Making the step from these principles to the Copernican principle, however, is an unjustified ideological leap.

The fact that “the Earth is the only world known so far to harbor life” rather speaks to me of its importance. If the Earth were not as small as it is, then its surface gravity would be too strong for life as we know it. If the Earth didn’t orbit a G-type star, the circumstellar habitable zone could easily be less stable. If our Sun were a member of an elliptical galaxy or closer to the center of our spiral galaxy, or even in the spiral arms rather than between them, interactions with other stars would be more likely, which could more easily disrupt the stability of our solar system. So many places in the universe are inhospitable to life. We live on a planet where life is possible. I think that is enough to challenge Sagan’s claim that we are deluded to think “we have some privileged position in the universe.” Authors Jay W. Richards and Guillermo Gonzalez of The Privileged Planet challenge Sagan and the Copernican principle with a thesis that not only is our planet well suited for life, but it is also well suited for discovery. Although I am unsatisfied with its presentation of the “intelligent design” view as scientific, I highly recommend watching the thought-provoking documentary and even reading the book.

The fact that in the Pale Blue Dot image the Earth lies in a sunbeam is indeed, as Sagan says, an effect of geometry and optics. Just from that, however, there is no way to prefer one philosophical view over another. The worldviews that clash over the Earth’s significance or insignificance are entrenched enough that I do not expect any amount of scientific discovery to settle the dispute. The science we discover certainly inspires wonder, and we need to keep doing science. We also need to reason more rigorously and integrate the different ways we can come to know things. By doing this, we can sort fact from opinion and identify any unjustified leap before falling for a conclusion that could lead us down a dark or deluded path.

I believe it is pertinent to close this post with a related quote from St. John Paul the Great: “If knowledge of the unmeasured dimensions of the cosmos has erased the dream that our planet or our solar system could be the physical center of the world, not by that is man diminished in his dignity” (translation from Italian).

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Total Lunar Eclipse on 1/31/2018

Total Lunar Eclipse on 1/31/2018

Interested in seeing the Earth’s shadow fall on the Moon on the 31st of this month? Here’s a simple and elegant representation by timeanddate.com showing where on Earth it will be visible from. This is a lunar eclipse. It will be total roughly 5-6am Pacific Time. Because a lunar eclipse can only happen at Full Moon, you can only see it if it’s nighttime where you’re at. Western North America, Pacific, Australia, and Eastern Asia, mark your calendars!

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The Origin of the Universe

The Origin of the Universe

The origin of the Universe is one of my favorite topics at the interface between science and faith. I’ve spoken on this several times (which I’ve kept track of on my Talks and Presentations page). The most recent occasion was the first time it was recorded. You can view it here. It took me a while to upload this because I wanted to find the right video-editing software to superimpose images I refer to. As this was the first time I’ve given this talk without an accompanying slideshow, I decided to provide handouts to the audience at least for my introduction, featuring the Hubble Deep Field. One of my goals for the next year is to record and produce a higher-quality video just for online viewing. For the time being, this is what I’m able to provide. The first half-hour is my talk; the second half-hour is Q&A.

Both science and faith have something to say about the origin of the Universe. 20th-century developments in physics enabled us to do scientific cosmology and investigate the properties of the Universe as a whole. Multiple pieces of evidence — such as the cosmological redshift, cosmic microwave background radiation, and abundances of primordial elements, to name a few — support the Big Bang cosmological model, which tells us that the Universe has been expanding for about 14 billion years. This, however, seems to clash with the creation account of Genesis. Do science and faith disagree here? Not necessarily. Genesis was not meant to be a physics textbook; certain passages do not have to be interpreted literally. Genesis tells us that God created the Universe out of nothing (ex nihilo) and that he created humans in his own image and likeness. These are philosophical and theological concepts. The Big Bang is a scientific model. Science, reason, and faith are all different ways of knowing truths that we need to learn how to integrate. Two truths cannot contradict each other. The same God that created the Cosmos can also enter it. He made the Universe intelligible because he wants us to know about it; yet he also wants us to know him. We don’t have to discredit our power of knowing Nature in order to discover God through Scripture. Neither do we have to throw away Scripture to accept all the new and exciting discoveries of Nature.   For a complete understanding of reality, we need both science and faith.

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